update NDC realization to run 2030+2035 NDC emissions targets by default and clean up + extend on switches for NDC variants by fschreyer · Pull Request #2289 · remindmodel/remind

fschreyer · 2026-02-18T17:07:02Z

Purpose of this PR

This PR works over the realization of the NDC scenario in REMIND. The main changes are:

change default NDC scenario to new scenario including 2030 and 2035 emissions targets derived from PBL data (scenario config change still to-do)
remove / add switches to run NDC variants
- cm_NDC_CO2PriceLimit
- cm_NDC_postTargetDevelopment
- cm_NDC_CO2PriceMinimum
- cm_NDC_TargetCheckConv
- cm_NDC_divergentScenario (removed)
clean-up NDC realization and improve documentation

Type of change

Indicate the items relevant for your PR by replacing ◻️ with ☑️.
Do not delete any lines. This makes it easier to understand which areas are affected by your changes and which are not.

Parts concerned

☑️: GAMS Code
◻️ R-scripts
◻️ Documentation (GAMS incode documentation, comments, tutorials)
◻️ Input data / CES parameters
◻️ Tests, CI/CD (continuous integration/deployment)
◻️ Configuration (switches in main.gms, default.cfg, and scenario_config*.csv files)
◻️ Other (please give a description)

Impact

◻️ Bug fix
◻️ Refactoring
☑️ New feature
◻️ Change of parameter values or input data (including CES parameters)
◻️ Minor change (default scenarios show only small differences)
◻️ Fundamental change of results of default scenarios

Checklist

Do not delete any line. Leave unfinished elements unchecked so others know how far along you are.
In the end all checkboxes must be ticked before you can merge.

I executed the automated model tests (make test) after my final commit and all tests pass (FAIL 0)
I adjusted the reporting in remind2 if and where it was needed
I adjusted the madrat packages (mrremind and other packages involved) for input data generation if and where it was needed
My code follows the coding etiquette
I explained my changes within the PR, particularly in hard-to-understand areas
I checked that the in-code documentation is up-to-date
I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
I updated the CHANGELOG.md correctly (added, changed, fixed, removed, input data/calibration)

Further information (optional)

Runs with these changes are here:
Comparison of results (what changes by this PR?):
/p/tmp/schreyer/Modeling/remind/Dev1/compScen-NDC_Current_vs_2030_vs_NDCallPF-2026-02-17_10.19.07-H12.pdf

New NDC is NDC_all_pf. Old NDC is SSP2-NDC-AMT.

…ion 2025_cond/uncond and improve documentation of NDC target versions

…p45_useSingleYearCloseTo as this is meanwhile done by switch cm_NDC_targetYear

…nd clean-up NDC post-target co2 price settings. This introduces new flags cm_NDC_CO2PriceLimit, cm_NDC_postTargetDevelopment, cm_NDC_CO2PriceMinimum

…_CO2PriceMinimum

… emissions targets should be convergence criterion. By default, runs do not require NDC target compliance

… NPi co2 price for all time steps

…DC realization always iterates carbon prices

…al NDC targets based on latest PBL data) and switch on targets for 2030 and 2035 by default

…SSP scenarios. Needs to be there until deleted in input data.

…oduced in main.gms

RahelMA

Great work, thank you! I just have minor documentation comments!

RahelMA · 2026-02-20T09:47:20Z

modules/45_carbonprice/NDC/datainput.gms

-    p45_taxCO2eqConvergenceYear = 3000;
-);
+*** initialize carbon price trajectory before target adjustment iterations by setting carbon price to NPi
+pm_taxCO2eq(t,regi) = p45_taxCO2eq_bau(t,regi);


Initializing on the NPi2025 is useful, have you check that we never are below? I just wonder if we also need a constraint NPI <= NDC e.g. with low 2035 NDC targets

This is taken care of by cm_NDC_CO2PriceMinimum = NPi which is the default setting now.

RahelMA · 2026-02-20T09:51:33Z

modules/45_carbonprice/NDC/datainput.gms

-Scalar p45_minRatioOfCoverageToMax                  "only targets whose coverage is this times p45_bestNDCcoverage are considered. Use 1 for only best [0..1]" /1.0/;
-Scalar p45_useSingleYearCloseTo                     "if 0: use all. If > 0: use only one single NDC target per country closest to this year (use 2030.4 to prefer 2030 over 2035 over 2025) [year]" /2030.4/;
+Scalar p45_minRatioOfCoverageToMax                  "only targets whose coverage is this times p45_bestNDCcoverage are considered. Use 1 for only best [0..1]" /0/;
+Scalar p45_useSingleYearCloseTo                     "if 0: use all. If > 0: use only one single NDC target per country closest to this year (use 2030.4 to prefer 2030 over 2035 over 2025) [year]" /0/;


Use NDC targets independent from coverage, top!

I think with your change you use all targets in the input data, I asume thats ok as we only have 2030 and 2035 for Emissions_2026_cond, for other versions this would cause an error (e.g. 2024 also includes some 2050 targets) ... maybe you want to add a little warning note?

The switch cm_NDC_targetYear = 2030, 2035 now only selects those two years.

RahelMA · 2026-02-20T09:53:13Z

modules/45_carbonprice/NDC/datainput.gms

-
-if (not sameas("%cm_NDC_version%","2018_uncond"),
-    p45_factorTargetyear(t,regi)$(sameas(regi,"LAM") AND sameas(t,"2030")) = p45_factorTargetyear(t,regi) + 0.2;
-    p45_factorTargetyear(t,regi)$(sameas(regi,"LAM") AND sameas(t,"2035")) = p45_factorTargetyear(t,regi) + 0.2;


With these deletions, older version may have problems, but that ok, as we will remove them this summer ;)

RahelMA · 2026-02-20T09:54:09Z

modules/45_carbonprice/NDC/declarations.gms

 p45_taxCO2eq_bau(ttot,all_regi)                          "level of CO2 taxes in business as usual run [T$/GtC]"
 pm_NDCEmiTargetDeviation(ttot,all_regi)                  "deviation of REMIND emissions to NDC target emissions in last iteration normalized to NDC target emissions [0-1]"
+$ifthen not "%cm_NDC_CO2PriceLimit%" == "off"
+p45_CO2PriceLimitNDC(ttot,all_regi)                       "Upper limit of CO2 price in NDC realization, read from switch cm_NDC_CO2PriceLimit [$/tCO2]" / %cm_NDC_CO2PriceLimit% /


so we currently set the price limit in the config, that's nice!

RahelMA · 2026-02-20T09:54:51Z

modules/45_carbonprice/NDC/not_used.txt

 pm_budgetDeviation,input,added by codeCheck
 pm_regionalBudget_absDevTol,input,added by codeCheck
 cm_startyear,input,not used
+sm_D2005_2_D2017,input,not used


why do we need to add this here? sm_D2005_2_D2017

Just a code check request. Probably I deleted code using this before.

RahelMA · 2026-02-20T10:02:08Z

modules/45_carbonprice/NDC/preloop.gms

+*#'  calculate level of emission target per REMIND region. It is componsed to two terms:
+*#'  1. Contribution of countries within REMIND region with NDC target: 
+*#'     share of emissions covered by NDC in particular region * REMIND NPI emissions in 2015 * (country-aggregated) relative NDC emissions target with respect to 2015
+*#'  2. Contribution of countries within REMIND region without NDC target:


Nice documentation

RahelMA · 2026-02-20T10:02:55Z

modules/45_carbonprice/NDC/preloop.gms

 p45_CO2eqwoLU_goal(p45_NDCyearSet(t,regi)) =
          p45_shareTarget(t,regi)     * p45_BAU_reg_emi_wo_LU_wo_bunkers("2015",regi) * p45_factorTargetyear(t,regi)    !! share with NDC target
-        + (1-p45_shareTarget(t,regi)) * p45_BAU_reg_emi_wo_LU_wo_bunkers(t,regi);            !! baseline for share of countries without NDC target
+        + (1-p45_shareTarget(t,regi)) * p45_BAU_reg_emi_wo_LU_wo_bunkers(t,regi);                                       !! baseline for share of countries without NDC target


I see it correctly, you have not changed the formula, right?

RahelMA · 2026-02-20T10:04:58Z

modules/80_optimization/nash/postsolve.gms

 $ifthen.NDC "%carbonprice%" == "NDC" 
+$ifthen.targetCheck  "%cm_NDC_TargetCheckConv%" == "on"
 *** additional criterion: Were NDC emissions targets reached?
 loop((t,regi)$pm_NDCEmiTargetDeviation(t,regi),


Could you please add the documentation what happens in pm_NDCEmiTargetDeviation?

Is this only checking if the target is reached?

RahelMA · 2026-02-20T10:06:19Z

main.gms

+*' *  (2026_uncond):              all NDCs independent of international financial support published until end of 2025 (PBL collection), note that for countries / regions with target ranges (e.g. EU 66-72% 2035 target) 
+*' *                              the less ambitious target is chosen even if it is strictly speaking not an unconditional NDC target
+*' *  (2024_cond_extrapol):       all NDCs conditional to international financial support published until August 31, 2024 with extrapolation of 2030 targets to 2035 targets for conutries without 2035 target
+*' *  (2024_uncond_extrapol):     all NDCs independent of international financial support published until August 31, 2024 with extrapolation of 2030 targets to 2035 targets for conutries without 2035 target


Great documentation!

RahelMA · 2026-02-20T10:07:33Z

main.gms

 *' * Note: including target years here does not mean they are automcatically considered in the carbonprice NDC realization. 
 *' * Depending on the p45_minRatioOfCoverageToMax parameter, each region receives the target year with the highest share of emissions covered under NDCs.
-$setglobal cm_NDC_targetYear  "2030"    !! def = "2030"
+$setglobal cm_NDC_targetYear  "2030, 2035"    !! def = "2030, 2035"


ah I see we only have 2030 and 2035, so you can ignore my comment before ;)

RahelMA · 2026-02-20T10:10:23Z

Could you please provide the config changes in a readable format using
comparescenconf!

fschreyer · 2026-02-20T12:30:40Z

Eventually, I realized I didn't need a scenario config change. I tested the new default NDC run here /p/tmp/schreyer/Modeling/remind/Dev1/output/SSP2-NDC_2026-02-20_10.02.30.

Felix Schreyer added 14 commits January 8, 2026 20:59

Merge branch 'develop' of github.com:remindmodel/remind into NpiNDC

7e89c24

add new NDC target version 2026_cond/uncond, remove intermediate vers…

7c51b58

…ion 2025_cond/uncond and improve documentation of NDC target versions

deactivate target year selection via p45_minRatioOfCoverageToMax and …

ee4a5ca

…p45_useSingleYearCloseTo as this is meanwhile done by switch cm_NDC_targetYear

introduce switch to limit co2 prices in NDC target years, work over a…

0d63ab4

…nd clean-up NDC post-target co2 price settings. This introduces new flags cm_NDC_CO2PriceLimit, cm_NDC_postTargetDevelopment, cm_NDC_CO2PriceMinimum

clean up and remove deprecated code in carbonprice NDC realization

17ec9da

fix bugs in implementation of cm_NDC_postTargetDevelopment and cm_NDC…

1359581

…_CO2PriceMinimum

add flag cm_NDC_TargetCheckConv to choose whether or not reaching NDC…

4440ea1

… emissions targets should be convergence criterion. By default, runs do not require NDC target compliance

remove deprecated cm_NDC_divergentScenario

6859c86

if cm_NDC_CO2PriceMinimum == NPi, set minimum co2 price of NDC run to…

fe5ed3d

… NPi co2 price for all time steps

remove cm_iterative_target_adj eq 3 condition in NDC realization as N…

8313451

…DC realization always iterates carbon prices

modify NDC_version set to acommodate new input data

e558e22

Merge branch 'develop' of github.com:remindmodel/remind into NpiNDC

79584b5

fix code check for carbonprice module

9feeffd

switch default setting of NDC run to NDC version 2026_cond (condition…

9d2bfb0

…al NDC targets based on latest PBL data) and switch on targets for 2030 and 2035 by default

fschreyer requested review from RahelMA and lea-hayez February 18, 2026 17:07

Felix Schreyer added 3 commits February 20, 2026 09:58

add old NDC versions again because they are still used in some other …

d97916c

…SSP scenarios. Needs to be there until deleted in input data.

remove quotation marks around default values of new NDC switches intr…

c510e90

…oduced in main.gms

add to CHANGELOG

d1b3912

fschreyer marked this pull request as ready for review February 20, 2026 09:46

RahelMA approved these changes Feb 20, 2026

View reviewed changes

improve documentation of NDC changes

c0219e7

fschreyer merged commit 23604eb into remindmodel:develop Feb 20, 2026
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RahelMA commented Feb 20, 2026

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fschreyer commented Feb 20, 2026

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fschreyer commented Feb 18, 2026 •

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